Production of a woven or knit fabric from a composite yarn composed of a spun yarn and a polyurethane elastic yarn in combination has been actively performed for providing stretch properties and improving texture, lightweight properties, and bulky feel. Typical examples of composite yarns obtained by combining a spun yarn and a polyurethane elastic yarn are a core spun yarn obtained by covering the surrounding of a core thread composed of a polyurethane elastic yarn by spinning cotton and twisting these, a single-covered yarn and a double-covered yarn obtained by winding a spun yarn once or repeatedly around a core thread composed of a polyurethane elastic yarn, and others. When a woven or knit fabric is produced by using these composite yarns, provision of stretch properties and an improvement in voluminosity to some degree are possible, however, in many cases, the woven or knit fabric is insufficient in softness, airy texture, lightweight properties, and bulky feel.
Other than the composite yarns, a method for making a yarn bulky by shrinking the yarn is also known, however, this method is applicable only to yarns using synthetic fiber such as acrylic fiber, and is difficult to apply to cotton fibers, so that this method lacks versatility.
Further, the twists of the spun yarn become a factor that spoils the texture, lightweight properties, and bulky feel, so that production of a woven or knit fabric by using a spun yarn with a reduced number of twists is widely adopted. As a method for reducing the number of twists, there is a method in which a spun yarn is produced by reducing the set number of twists in fine spinning in the spinning process, etc., however, due to the reduced number of twists, pilling and friction (or abrasion) easily occur and fiber that falls out at the time of washing easily increases although the texture is improved.
Further, Japanese Patent Application Laid-Open Publication No. 2006-225797 (JP-2006-225797A, Patent Document 1) and Japanese Patent Application Laid-Open Publication No. 2007-154339 (JP-2007-154339A, Patent Document 2) disclose a method in which a composite twisted yarn is produced by twisting a spun yarn and a water-soluble yarn to the number of twists 0.5 to 1.0 times the number of twists of the spun yarn in an opposite direction to the twisting direction of the spun yarn, a woven or knit fabric is produced by using this composite twisted yarn, and then the water-soluble yarn is dissolved. However, with this method, although a woven or knit fabric with good texture is obtained, lightweight properties and bulkiness cannot be sufficiently obtained due to the crossing points of the yarns and interlace portions (e.g., contacts between warp yarns and weft yarns in a woven fabric, overlapping portions of loops in a knit fabric), so that pilling and friction easily occur, and fiber that falls out at the time of washing easily increases.
On the other hand, Japanese Patent No. 4393357 (JP-4393357B, Patent Document 3) discloses a composite twisted yarn produced by twisting a spun yarn and a water-soluble yarn to the number of twists 1.3 to 3 times the number of twists of the spun yarn in an opposite direction to the twisting direction of the spun yarn, and a woven or knit fabric produced by providing a woven or knit fabric composed of the composite yarn and then dissolving and removing the water-soluble yarn in water. This woven or knit fabric is excellent in texture, lightweight properties, and air permeability, and has stretch properties.
However, this composite yarn includes a water-soluble yarn, and a twisting torque thereof is so great that the composite yarn cannot be used for weaving and knitting, therefore, it requires a heat-setting process such as steam setting and a process for removing the water-soluble yarn dissolved by heat setting. Further, even if the yarn is subject to heat setting, warping properties and weaving and knitting properties thereof are not sufficient, and for example, when yarn breakage occurs during weaving, the tension generates a torque and causes the yarn to twist (curl), and it is difficult to restart the weaving/knitting machine. Further, due to the strong torque, for example, if the yarn is used for single knitting, welt skew occurs, and fine knitting is difficult, and yarn breakage easily occurs.
The water-soluble yarn is included in the composite twisted yarn, so that twisted yarns adhere to each other according to heat setting, and if the composite twisted yarn is preserved in the form of a wound yarn for a long period of time, twisted yarns easily adhere to each other, so that the preservation stability is low particularly in a humid environment.
When a dyed yarn is used, a composite twisted yarn is made of the dyed yarn and a water-soluble yarn, and after a woven or knit fabric is produced by using this composite twisted yarn, the water-soluble yarn must be dissolved and removed, however, in the removal by dissolution, the color of the dyed yarn may change or fade, and in particular, it is difficult to remove by dissolution the water-soluble yarn at 95° C. from a woven or knit fabric containing the water-soluble yarn and a cotton yarn directly colored with a dye.
Further, in the method in which the water-soluble yarn in the woven or knit fabric is removed, the water-soluble yarn is removed by dissolution in a state where the composite twisted yarn is confined (or bound) within the woven or knit fabric, so that lightweight properties and bulkiness are not sufficient at crossing points and interlace portions of the yarns in the woven or knit fabric.